Waste generated by mineral extraction is globally associated with environmental disturbances due to its deleterious effect on water resources. However, research focused on the influence of mine tailings resulting from the extraction of semi-precious stones on fluvial systems is still incipient in the environmental literature. From this perspective, this study quantified the average concentrations of major oxides present in the fine fractions of the sediment samples from the Várzea river, in the State of Rio Grande do Sul, southern Brazil, using wavelength dispersive X-ray fluorescence spectrometry. This region is acknowledged as the largest rock amethyst mining area in the world. Additionally, geochemical indices were established to characterize potential sources of production, maturity, degree of weathering, and sediment pollution. To evaluate the influence of mine tailings on the Várzea river sediments, the contents of Al2O3, Fe2O3, MnO, P2O5, CaO, SiO2, K2O, CuO, ZnO, and TiO2 major oxides present in sediment samples were determined and compared to the local background values; the values varied significantly (p < 0.05), classifying them as polluted and medium polluted. Also, the sediment samples with evident characteristics of extreme chemical weathering consist mainly of clay minerals and mafic igneous rocks, and similarities were found between sediment samples and tailings from the mineral extraction zone. The Principal Component Analysis and the cluster analysis also suggest the existence of three distinct mineral oxide groups, differentiating the zones leaving and upstream the mining zone from the other sampling points.
Energy availability has direct influence over hydrological cycle, climate and preciptation. The determination of net radiation balance (Rn) and the spacial and temporal recognition of water availability allow establishing guidelines and planning the implementation of public resource management policies. The objective of this study was to analyze the water balance and net radiation balance of the year 2017 at two experimental sites in the state of Rondônia (RO), Brazil: an Amazon rainforest area located in the Jaru Biological Reserve (REBIO) and a pasture area (FNS) located in the municipality of Ouro Preto d’Oeste, near the forest área. The data were obtained from the REBIO climatological station, in the municipality of Ji-Paraná-RO, belonging to the experimental sites. Calculations for evapotranspiration potential were based on Thornthwaite and Mather’s method. The "Eddy Covariance" method was used to obtain the radiation balance. The forest system presented greater energy availability in the rainy season and higher evapotranspiration balance when compared to the pasture area. Water balance extract analysis pointed to water stress in pasture area, opposite to the forest area, which indicates that conversion of native forest to pasture is a process capable to compromise the availability of water resources and alter climatic aspects.
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